CN111999241A

CN111999241A - Road surface friction coefficient prediction system

Info

Publication number: CN111999241A
Application number: CN202010459708.9A
Authority: CN
Inventors: 挂樋聪美
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 2019-05-27
Filing date: 2020-05-27
Publication date: 2020-11-27
Also published as: US11276305B2; DE102020113937A1; DE102020113936A1; US20200380862A1

Abstract

The invention provides a road surface friction coefficient prediction system, comprising: an external information acquisition unit that acquires external information; a tire condition coefficient calculation unit that acquires tire information indicating a condition of a tire of a vehicle; and a friction coefficient prediction unit that predicts a friction coefficient between the tire and the road surface based on the tire condition coefficient acquired by the tire condition coefficient calculation unit and the road surface condition acquired by the external information acquisition unit, the friction coefficient prediction unit predicting a friction coefficient of the road surface ahead of the vehicle in the traveling direction.

Description

Road surface friction coefficient prediction system

Technical Field

The present disclosure relates to a road surface friction coefficient prediction system that predicts a friction coefficient of a road surface.

Background

A road surface friction coefficient prediction system described in japanese patent application laid-open No. 2018-004417 predicts a friction coefficient of a road surface based on a state of a tire of a vehicle. The road surface friction coefficient prediction system is provided with: a vibration detection unit that detects vibration of the tire during running; a vibration waveform detection unit that detects a time-varying waveform of vibration of the tire; a road surface state discrimination unit for discriminating the state of the road surface based on the time-varying waveform; and a tire condition detection unit for acquiring the condition information of the tire. The road surface state discriminating unit discriminates the state of the road surface from a discrimination parameter for discriminating the state of the road surface obtained from the vibration waveform and the state information of the tire. According to this configuration, the road surface condition can be determined with high accuracy even when the tire condition changes.

However, in this road surface friction coefficient prediction system, since the road surface state is determined based on the vibration of the tire during running, when the road surface state changes during running, the friction coefficient of the road surface may not be accurately predicted.

Disclosure of Invention

One embodiment of the present disclosure relates to a road surface friction coefficient prediction system capable of accurately predicting a friction coefficient of a road surface even when a road surface state changes.

According to one embodiment of the present disclosure, a road surface friction coefficient prediction system includes: an external information acquisition unit that acquires external information relating to an interference element that affects a condition of a road surface on which a target vehicle is traveling; a tire information acquisition unit that acquires tire information indicating a condition of a tire of the target vehicle; and a friction coefficient prediction unit that predicts a friction coefficient between the tire and the road surface based on the tire information acquired by the tire information acquisition unit and the external information acquired by the external information acquisition unit, wherein the friction coefficient prediction unit predicts a friction coefficient of a road surface ahead of the target vehicle in a traveling direction.

Drawings

Fig. 1 is a block diagram showing an example of the overall configuration of a tire condition determination system according to an embodiment of the present disclosure.

Fig. 2 is a block diagram showing a configuration example of the own vehicle of fig. 1.

Fig. 3 is a block diagram showing a configuration example of the information collection server of fig. 1.

Fig. 4A is a graph showing an example of a reference map showing a relationship between a road surface condition and a friction coefficient.

Fig. 4B is a graph showing an example of a statistical map of the relationship between the tire condition coefficient and the friction coefficient.

Fig. 5 is a table showing an example of collected data collected by the information collection server of fig. 1.

Fig. 6 is a flowchart showing an example of an operation performed by the control unit of the vehicle and the information collection server shown in fig. 1.

Fig. 7 is a block diagram showing an example of the overall configuration of a road surface friction coefficient prediction system according to another embodiment of the present disclosure.

Fig. 8 is a block diagram showing a configuration example of the own vehicle shown in fig. 7.

Fig. 9 is a block diagram showing a configuration example of the information collection server of fig. 7.

Fig. 10A is a graph showing an example of a reference map showing a relationship between a road surface condition and a friction coefficient.

Fig. 10B is a graph showing an example of a statistical map of the relationship between the tire condition coefficient and the friction coefficient.

Fig. 11 is a table showing an example of collected data collected by the information collection server of fig. 7.

Fig. 12 is a flowchart showing an example of an operation performed by the control unit of the host vehicle and the information collection server shown in fig. 7.

Fig. 13 is a configuration diagram showing an example of the overall configuration of a traction performance evaluation system according to another embodiment of the present disclosure.

Fig. 14 is a block diagram showing a schematic configuration example of the host vehicle shown in fig. 13.

Fig. 15 is a block diagram showing a configuration example of the control device of fig. 14.

Fig. 16 is an example of collected data collected by the information collection server of fig. 13.

Fig. 17 is a block diagram showing a configuration example of the information collection server of fig. 13.

Fig. 18 is a table showing an example of a statistical map of the relationship between the command torque and the slip ratio.

Fig. 19 is a graph showing transition of the rank information with time.

Fig. 20 is a statistical chart showing a relationship between slip ratio and elapsed time.

Fig. 21 is a graph showing an example of an I-T characteristic map showing a relationship between the command current value and the command torque.

Fig. 22 is a flowchart showing an example of an operation performed by the control unit of the host vehicle and the information collection server shown in fig. 13.

Detailed Description

[ first embodiment ]

A first embodiment of the present disclosure will be described with reference to fig. 1 to 6. The embodiments described below are embodiments shown as preferred specific examples for implementing aspects of the present disclosure, and include portions specifically illustrating various technical matters that are technically preferred, but the technical scope of the present disclosure is not limited to the specific embodiments.

Fig. 1 is a configuration diagram showing a schematic configuration example of the entire tire condition determination system according to the first embodiment of the present disclosure.

As shown in fig. 1, a tire condition determination system SYS1 includes: a vehicle 1 to be a determination target of a tire state; a plurality of other vehicles 5; and an external device 9 communicably connected to the host vehicle 1 and the plurality of other vehicles 5 via a wireless communication network 90.

In the present embodiment, the host vehicle 1 is distinguished from the plurality of other vehicles 5 for convenience of explanation, but the plurality of other vehicles 5 may be targets for determining the tire state, and the host vehicle 1 and the plurality of other vehicles 5 correspond to "target vehicles" in the present disclosure. The model, year, model, and the like of the host vehicle 1 and the plurality of other vehicles 5 are arbitrary, and are not particularly limited.

The external device 9 includes: an information collection server 6 that collects vehicle information transmitted from the host vehicle 1 and the plurality of other vehicles 5; a weather information server 81; a road information server 82; and a Global Positioning System (GPS) 83.

The weather information server 81 is a server that provides weather information of japan acquired from weather stations and the like in various places. The road information server 82 is a server that provides information indicating a road state (for example, a paved road) according to the current position where the vehicle is traveling. The weather information provided by the weather information server 81 and the road information provided by the road information server 82 are examples of disturbance elements that affect the condition of the road surface on which the vehicle is traveling.

Fig. 2 is a block diagram showing the structure of the vehicle 1. Fig. 3 is a block diagram showing the configuration of the information collection server 6 of the external device 9. As shown in fig. 2, the host vehicle 1 includes: a communication unit 21 that transmits and receives information to and from the plurality of other vehicles 5 and the external device 9; a control unit 3 that controls the vehicle 1; a display unit 22 for displaying information output from the control unit 3; a travel information detection unit 23 that detects information relating to the travel state of the host vehicle 1; a position detection unit 24 that detects the current position of the host vehicle 1 based on satellite signals from the GPS 83; and a storage unit 4 including a Memory element such as a Read Only Memory (ROM) or a Random Access Memory (RAM). The plurality of other vehicles 5 also have the same configuration as the host vehicle 1.

The communication unit 21 is an electronic control device that transmits and receives information to and from a communication destination other than the host vehicle 1 by communicating with the communication destination via the wireless communication network 90. The Communication unit 21 includes a Communication Module such as a Data Communication Module (DCM).

The display unit 22 displays information output from the control unit 3. The display unit 22 is a display such as a liquid crystal display or an organic electroluminescence display, and may function as a display unit of a car navigation system or may be provided on a console panel of a vehicle.

The travel information detection unit 23 includes a plurality of sensors for acquiring parameters of the travel state of the host vehicle 1, such as a vehicle speed sensor for acquiring a vehicle speed and a steering angle sensor.

The position detection unit 24 is a GPS receiver that acquires position information indicating the current position of the vehicle 1, and acquires the current position information (such as the longitude and latitude) of the vehicle 1 using a satellite positioning system.

The control Unit 3 includes a Central Processing Unit (CPU) and peripheral circuits thereof. The control unit 3 functions as each means such as a friction coefficient estimating means 33 described later by executing the program 41 stored in the storage unit 4.

The control unit 3 includes an external information acquisition unit 31, a positional information acquisition unit 32, a friction coefficient estimation unit 33, a tire condition coefficient calculation unit 34, a transmission unit 35, a statistical map acquisition unit 36, a tire condition evaluation unit 37, and a notification unit 38.

The external information acquisition unit 31 estimates the road surface condition based on weather information provided by the weather information server 81 of the external device 9. For example, the external information acquisition unit 31 estimates that the road surface condition is dry when the weather information is fine, and estimates that the road surface condition is wet when the weather information is rainy. The external information acquisition unit 31 acquires information indicating a road state (a paved road or an unpaved road) based on the road information provided by the road information server 82.

The position information acquisition unit 32 acquires the position information generated by the position detection unit 24.

The friction coefficient estimating unit 33 estimates the friction coefficient between the tire of the vehicle and the road surface based on the running information relating to the running state of the vehicle detected by the running information detecting unit 23. The friction coefficient can be estimated based on, for example, the difference between the average rotational speed of the front left and right wheels and the average rotational speed of the rear left and right wheels in the steady running state.

The tire condition coefficient calculation unit 34 calculates a tire condition coefficient by comparing the estimated friction coefficient estimated by the friction coefficient estimation unit 33 with a reference friction coefficient corresponding to the road surface condition, which indicates the slip tendency of the tire.

The reference friction coefficient can be obtained, for example, by referring to a reference map 42 (shown in fig. 4A) stored in advance in the storage unit 4. The reference map 42 includes reference friction coefficients set for each road surface condition (dry, wet, and snow cover), and the values of the reference friction coefficients are determined by performance evaluation at the time of factory shipment, for example. The tire condition coefficient calculation unit 34 acquires the reference friction coefficient from the reference map 42 based on the road surface condition determined by the external information acquisition unit 31. The reference friction coefficient may be set for each road state. This makes it possible to obtain a reference friction coefficient according to a more detailed road surface condition.

Here, the tire condition coefficient is an index value that affects the degree of slip of the vehicle due to the state of the tire (wear of the tire, air pressure, etc.), and can be obtained, for example, as a ratio of an estimated friction coefficient to a reference friction coefficient (tire condition coefficient is estimated friction coefficient/reference friction coefficient). That is, the larger the value of the tire condition coefficient is, the more difficult the state of the tire of the running vehicle is to slip.

The transmitting unit 35 transmits information indicating the slip factor of the tire to the information collection server 6 via the communication unit 21. In the present embodiment, the transmission unit 35 generates transmission data based on the friction coefficient estimated by the friction coefficient estimation unit 33, the tire condition coefficient calculated by the tire condition coefficient calculation unit 34, vehicle information (vehicle ID, vehicle type, vehicle speed, and the like) related to the own vehicle 1, position information, road state, and road surface condition. Then, the transmission unit 35 transmits the transmission data to the information collecting server 6 of the external device 9. This transmission data corresponds to a part of the collected data 60 collected by the information collecting server 6.

The information collection server 6 receives data similar to the transmission data transmitted by the transmission unit 35 from the plurality of other vehicles 5, and collects the received data as the collected data 60. Fig. 5 is a table showing an example of the collected data 60. As shown in fig. 5, the collected data 60 has, as items, a vehicle ID for identifying the vehicle, information on the type of the vehicle, position information indicating the current position where the vehicle is traveling, a road state and a road surface condition at a position indicated by the position information, and a friction coefficient and a tire condition coefficient calculated for each vehicle. The items of the collected data 60 are not limited, and the collected data 60 may have information such as the measurement date and time and the travel distance as items.

The statistical map acquisition unit 36 of the control unit 3 acquires the statistical map 72 generated by the statistical map generation unit 53 of the information collection server 6, which will be described later. Fig. 4B is a graph showing an example of the statistical map 72. The statistical map 72 is set with a standard value O and a first threshold value S, which are obtained by correlating the tire condition coefficient and the friction coefficient μ₁And a second threshold value S₂. The statistical map 72 is not limited to this, as long as it is a map that can evaluate the slip tendency of the tires of the vehicle, and may be, for example, a map in which the slip ratio is associated with the tire condition coefficient, or may be data in which the vehicle speed is associated with the tire condition coefficient.

The standard value O is a value predetermined based on, for example, evaluation of the performance of the vehicle at the time of factory shipment. First threshold value S₁And a second threshold S₂For example, the value is determined by mapping the tire condition coefficient and the friction coefficient μ of the collected data 60 and using a statistical method for the data obtained by mapping. First threshold value S₁And a second threshold S₂The standard value O deviates from the predetermined value. First threshold value S₁And a second threshold S₂The value of the friction coefficient mu with respect to the tire condition coefficient may be smaller than the standard value O, and the second threshold value S₂Is greater than a first threshold value S₁Deviated from the standard value O.

Here, in the statistical map 72, the friction coefficient μ is made to be larger than the second threshold value S₂The small area is set as the first zone A, which will be defined by the first threshold S₁And a second threshold S₂The enclosed region is set as a second zone B which is defined by a first threshold S₁The third zone C is an area surrounded by the standard value O, and the fourth zone D is an area having a friction coefficient mu larger than the standard value O. For example, when the value of the friction coefficient corresponding to the tire condition coefficient is present in the first zone a, the vehicle is in a state of being likely to slip because the friction coefficient μ is smaller than the standard value O, and when the value is present in the fourth zone DSince the friction coefficient μ is larger than the standard value O, the vehicle is in a state of being hard to slip.

The tire condition evaluation unit 37 determines grade information, which is an evaluation index indicating the slip tendency of the tires of the host vehicle 1, by referring to the acquired statistical map 72. More specifically, the tire condition evaluation unit 37 maps the estimated friction coefficient estimated by the friction coefficient estimation unit 33 and the tire condition coefficient calculated by the tire condition coefficient calculation unit 34 to the statistical map 72, and determines the grade information based on the region on the statistical map 72 where the data obtained by mapping exists.

The tire condition evaluation unit 37 sets the grade information to grade a (slip level: large) when the mapped data exists in the first zone a, sets the grade information to grade B (slip level: medium) when the target data exists in the second zone B, and sets the grade information to grade C (slip level: small) when the target data exists in the third zone C, for example. In this way, the tire condition evaluation unit 37 determines the slip tendency of the own vehicle 1 based on the statistical map 72 generated from the collected data 60 relating to the plurality of other vehicles 5, and therefore can objectively evaluate the slip tendency of the tires of the own vehicle 1.

The information collection server 6 of the external device 9 may execute the functions of the tire condition coefficient calculation unit 34 and the tire condition evaluation unit 37. The tire condition coefficient calculation unit 34 and the tire condition evaluation unit 37 correspond to a "tire condition determination unit" of the present disclosure.

The notification unit 38 notifies the driver of the grade information obtained as a result of the determination by the tire condition evaluation unit 37. The notification unit 38 displays inspection information indicating, for example, replacement of a tire, deterioration of a vehicle, and the like, on the display unit 22 as caution information indicating that the tire is likely to slip, thereby notifying the driver. This can prompt the driver to drive safely.

As shown in fig. 3, the information collection server 6 includes: a communication unit 61 that transmits and receives information to and from the host vehicle 1 and the plurality of other vehicles 5; a control unit 62 for executing arithmetic processing based on the information collected via the communication unit 61; and a storage unit 63 for storing the program 71 executed by the control unit 62.

The control unit 62 of the information collection server 6 includes a reception unit 51 that receives the collected data 60 via the communication unit 61, a collected data extraction unit 52 that extracts data from the collected data 60 under a predetermined extraction condition, a statistical map generation unit 53 that generates a statistical map 72 based on the extracted data extracted by the collected data extraction unit 52, a storage unit 54 that stores the generated statistical map 72 in the storage unit 63, and a transmission unit 55 that transmits the statistical map 72 to the vehicle.

The collected data extraction unit 52 extracts data having the same vehicle type and position information as the host vehicle 1 and the same road surface condition as the host vehicle 1 from the collected data 60. The extraction conditions are not limited to these, and for example, the collected data extraction unit 52 may extract data of at least the same vehicle type as the host vehicle 1, or may extract data of at least the same position information as the host vehicle 1.

The statistical map generating unit 53 generates the statistical map 72 based on the tire condition coefficients and the friction coefficients of the plurality of pieces of extracted data extracted by the collected data extracting unit 52.

The transmission unit 55 reads the statistical map 72 from the storage unit 63, and transmits transmission data generated based on the read statistical map 72 to the host vehicle 1 through the communication unit 61.

Next, the processing of the tire condition determination system SYS1 according to the present embodiment will be described with reference to fig. 6. Fig. 6 is a flowchart showing an example of processing performed by the control unit 3 of the vehicle 1 and the control unit 62 of the information collection server 6.

The control unit 3 of the host vehicle 1 first acquires the position information indicating the current position of the host vehicle 1 generated by the position detection unit 24 (step S10), estimates the road surface conditions (dry, wet, and snow) based on the weather information acquired from the weather information server 81 of the external device 9, and estimates the road state based on the road information (paved and unpaved) acquired from the road information server 82 (step S11).

Next, the controller 3 of the host vehicle 1 estimates the road surface friction coefficient between the tire and the road surface based on the travel information indicating the travel state of the host vehicle 1 acquired from the travel information detector 23 (step S12), and calculates the tire condition coefficient based on the estimated friction coefficient and the reference friction coefficient of the reference map 42 stored in the storage unit 4 (step S13). The control unit 3 transmits the estimated friction coefficient and the tire condition coefficient calculated as described above and vehicle information (such as a vehicle ID, a vehicle type, and a vehicle speed) relating to the host vehicle 1 to the information collection server 6 of the external device 9 (step S14).

The control unit 62 of the information collection server 6 receives the collected data 60 transmitted from the own vehicle 1 and the plurality of other vehicles 5 (step S19), and generates the statistical map 72 based on the collected data 60 (step S20). The controller 62 stores the generated statistical map 72 in the storage 63 (step S21), and transmits the statistical map 72 to the vehicle (step S22). This ends the processing of the information collection server 6.

The control unit 3 acquires the statistical map 72 transmitted from the information collection server 6 (step S15), and obtains grade information as an evaluation index of the slip tendency of the tire condition of the vehicle 1 by referring to the acquired statistical map 72 (step S16). If the level information is the level a or the level B (step S17), the control unit 3 notifies the driver of the attention information indicating that the tire is in the slip-prone state (step S18). The determination condition in step S17 is not limited to this, and for example, the attention information may be notified only when the rank information is a, or the attention information of different contents may be notified when the rank is a and when the rank is B. On the other hand, if the level information is not level a or level B, the control unit 3 ends the processing as it is.

(action and Effect of the embodiment)

According to the embodiment described above, the tire condition determination system SYS1 determines the easy slip degree of the tire of the host vehicle 1 based on the tire condition coefficient indicating the easy slip degree of the tire obtained by comparing the reference friction coefficient indicating the easy slip degree of the tire according to the road surface condition and the friction coefficient estimated by the friction coefficient estimation means, and therefore can grasp the easy slip degree of the tire in consideration of external factors. Thus, the tire condition determination system SYS1 can accurately grasp the slip factor of the tire.

Further, according to the present embodiment, the tire condition determination system SYS1 notifies the driver of the rank information that ranks the degree of easy slip of the tire based on the statistical map 72 generated based on the tire condition coefficients and the friction coefficients of the plurality of other vehicles 5 that are the same vehicle type and travel at the same position as the host vehicle 1, and therefore can provide the driver with objective information indicating the degree of easy slip of the tire. This can prompt the driver to drive safely, and can prevent an accident in the future.

[ second embodiment ]

A second embodiment of the present disclosure will be described with reference to fig. 7 to 12.

Fig. 7 is a block diagram showing a schematic configuration of the entire road surface friction coefficient prediction system according to the second embodiment of the present disclosure.

As shown in fig. 7, a road surface friction coefficient prediction system SYS101 includes: a host vehicle 101 to be a determination target of a tire state; a plurality of other vehicles 105; and an external device 109 communicably connected to the host vehicle 101 and the plurality of other vehicles 105 via the wireless communication network 190.

In the present embodiment, the host vehicle 101 and the plurality of other vehicles 105 are distinguished with respect to the vehicle for convenience of explanation, but the plurality of other vehicles 105 may be targets for determining the tire state, and the host vehicle 101 and the plurality of other vehicles 105 correspond to "target vehicles" in the present disclosure.

The external device 109 includes: an information collection server 106 that collects vehicle information of the host vehicle 101 and the plurality of other vehicles 105; a weather information server 181; a road information server 182; and a GPS 183.

The weather information server 181 is a server that provides weather information of japan acquired from weather stations and the like in various places. The road information server 182 is a server that provides information indicating the road state of an unpaved road, a paved road, or the like around the current position where the vehicle is traveling. The weather information provided by the weather information server 181 and the road information provided by the road information server 182 are examples of disturbance elements that affect the condition of the road surface on which the vehicle is traveling.

Fig. 8 is a block diagram showing the structure of the vehicle 101. Fig. 9 is a block diagram showing the configuration of the information collection server 106 of the external device 109. As shown in fig. 8, the host vehicle 101 includes: a communication unit 121 that transmits and receives information to and from the plurality of other vehicles 105 and the external device 109; a control unit 103 that controls the host vehicle 101; a display unit 122 for displaying information output from the control unit 103; a travel information detection unit 123 that detects information relating to the travel state of the host vehicle 101; a position detection unit 124 that detects the current position of the host vehicle 101 based on satellite signals from the GPS 183; and a storage unit 10 including a storage element such as a ROM or a RAM. The plurality of other vehicles 105 also have the same configuration as the host vehicle 101.

The communication unit 121 is an electronic control device that transmits and receives information to and from a communication destination other than the host vehicle 101 by communicating with the communication destination via the wireless communication network 190. The communication unit 121 is constituted by a communication module such as DCM, for example.

The display unit 122 displays information output from the control unit 103. The display unit 122 is a display such as a liquid crystal display or an organic EL display, and may function as a display unit of a car navigation system or may be provided on a console panel of a vehicle.

The travel information detection unit 123 includes a plurality of sensors for acquiring parameters of the travel state of the host vehicle 101, such as a vehicle speed sensor for acquiring a vehicle speed and a steering angle sensor.

The position detection unit 124 is a GPS receiver configured to acquire position information indicating the current position of the vehicle 101, and is a GPS receiver configured to acquire the current position information (such as the longitude and latitude) of the vehicle 101 using a satellite positioning system.

The control unit 103 includes a CPU and its peripheral circuits. The control unit 103 functions as each unit such as a friction coefficient calculation unit 133 described later by executing the program 141 stored in the storage unit 104.

Control unit 103 includes external information acquisition section 131, position information acquisition section 132, friction coefficient calculation section 133, tire condition coefficient calculation section 134, friction coefficient prediction section 135, transmission section 136, statistical map acquisition section 137, tire state evaluation section 138, and notification section 139.

The external information acquisition unit 131 estimates the road surface condition based on weather information provided by the weather information server 181 of the external device 109. For example, the external information acquisition unit 131 estimates that the road surface condition is dry when the weather information is fine, and estimates that the road surface condition is wet when the weather information is rainy. Then, the external information acquisition unit 131 acquires information indicating a road state (a paved road or an unpaved road) based on the road information provided by the road information server 182.

Position information acquisition section 132 acquires position information generated by position detection unit 124.

The friction coefficient calculation unit 133 calculates a road surface friction coefficient at the travel position based on the travel information relating to the travel state of the vehicle detected by the travel information detection portion 123. The friction coefficient may be calculated based on the difference between the average rotational speed of the front left and right wheels and the average rotational speed of the rear left and right wheels in a steady running state, for example.

The tire condition coefficient calculation unit 134 calculates a tire condition coefficient by comparing the friction coefficient calculated by the friction coefficient calculation unit 133 with a reference friction coefficient corresponding to the road surface condition, which indicates the slip tendency of the tire.

The tire condition coefficient calculation unit 134 can obtain the reference friction coefficient from, for example, a reference map 142 (shown in fig. 10A) stored in advance in the storage unit 104. The reference friction coefficient is a friction coefficient set for each road surface condition (dry, wet, snow cover), and is a value determined by performance evaluation at the time of factory shipment, for example. Tire condition coefficient calculation section 134 acquires a reference friction coefficient by comparing the information on the road surface condition estimated by external information acquisition section 131 with reference map 142. In addition to the road surface condition, the reference friction coefficient may be set in the reference map 142 according to each road state. This prevents the deviation of the reference friction coefficient due to the difference in road conditions.

Here, the tire condition coefficient is an index value that affects the degree of hydroplaning of the vehicle due to the state of the tire (wear of the tire, air pressure, etc.), and is tire information indicating the condition of the tire of the vehicle. The tire condition coefficient can be obtained, for example, as the ratio of the reference friction coefficient to the calculated friction coefficient (tire condition coefficient: calculated friction coefficient/reference friction coefficient). That is, the larger the value of the tire condition coefficient is, the more difficult the state of the tire of the running vehicle is to slip. The tire condition coefficient calculation unit 134 is an example of the "tire information acquisition unit" in the present disclosure.

The friction coefficient prediction unit 135 predicts the road surface friction coefficient ahead in the vehicle traveling direction based on the tire condition coefficient calculated by the tire condition coefficient calculation unit 134 and the road surface condition or road state acquired by the external information acquisition unit 131.

More specifically, friction coefficient prediction section 135 obtains a reference friction coefficient corresponding to the road surface condition in the forward direction of the vehicle, and multiplies the reference friction coefficient by the tire condition coefficient to calculate a predicted friction coefficient in the forward direction of the vehicle. The reference friction coefficient corresponding to the road surface condition in the forward direction can be obtained by acquiring information on the road surface condition (dry, wet, snow) at the position in the forward direction by the external information acquisition means 131 and the position information acquisition means 132, and comparing the acquired information on the road surface condition with the reference map 142.

In the calculation of the predicted friction coefficient by the friction coefficient prediction unit 135, the road surface friction coefficients of a plurality of front vehicles that are the same vehicle type as the host vehicle 101 and travel at the same position as the position where the host vehicle 101 travels may be used as the reference friction coefficient. The road surface friction coefficients of the plurality of preceding vehicles are statistical values (for example, average values or the like) obtained by a statistical method, for example.

The transmitting unit 136 transmits information indicating the slip factor of the tire to the information collection server 106 via the communication unit 121. In the present embodiment, the transmission unit 136 generates transmission data based on the predicted friction coefficient predicted by the friction coefficient prediction unit 135, the tire condition coefficient calculated by the tire condition coefficient calculation unit 134, vehicle information (vehicle ID, vehicle type, vehicle speed, and the like) related to the own vehicle 101, position information, road state, and road surface condition. Then, the transmission unit 136 transmits the transmission data to the information collection server 106 of the external device 109. The transmission data corresponds to a part of the collected data 160 collected by the information collection server 106.

The information collection server 106 receives the same data as the transmission data transmitted by the transmission unit 136 from the plurality of other vehicles 105, and collects the received data as the collected data 160. Fig. 11 is a table showing an example of the collected data 160. As shown in fig. 11, the collected data 160 has, as items, a vehicle ID for identifying the vehicle, information on the type of the vehicle, position information indicating the current position where the vehicle is traveling, a road state and a road surface condition at a position indicated by the position information, and a friction coefficient and a tire condition coefficient calculated for each vehicle. The items of the collected data 160 are merely examples, and are not limited to these, and may include information such as the measurement date and time and the travel distance.

The statistical map acquisition unit 137 of the control unit 103 acquires the statistical map 172 generated by the statistical map generation unit 153 of the information collection server 106, which will be described later. Fig. 10B shows an example of the statistical map 172. The statistical map 172 is set with a standard value O and a first threshold value S, which are obtained by correlating the tire condition coefficient and the friction coefficient μ₁And a second threshold S₂. The statistical map 172 is not limited to this as long as it can evaluate the degree of easy slip of the tire of the vehicle, and may be a map obtained by relating the slip ratio to the tire condition coefficient, or may be data obtained by relating the vehicle speed to the tire condition coefficient.

The standard value O is, for example, a value determined based on the performance evaluation of the vehicle at the time of factory shipment. First threshold value S₁And a second threshold S₂For example, the tire condition coefficient and the friction coefficient μ of the collected data 160 are mapped and correlatedThe data obtained by the vertical mapping is a value determined by using a statistical method. First threshold value S₁And a second threshold S₂The standard value O deviates from the predetermined value. First threshold value S₁And a second threshold S₂The value of the friction coefficient mu with respect to the tire condition coefficient may be smaller than the standard value O, and the second threshold value S₂Is greater than a first threshold value S₁Deviated from the standard value O.

Here, in the statistical map 172, the friction coefficient μ is made to be larger than the second threshold value S₂The small area is set as the first zone A, which will be defined by the first threshold S₁And a second threshold S₂The enclosed region is set as a second zone B which is defined by a first threshold S₁The third zone C is an area surrounded by the standard value O, and the fourth zone D is an area having a friction coefficient mu larger than the standard value O. For example, when the value of the friction coefficient μ corresponding to the tire condition coefficient is present in the first zone a, the vehicle is in a state of being easy to slip because the friction coefficient is smaller than the standard value O, and when the value is present in the fourth zone D, the vehicle is in a state of being difficult to slip because the friction coefficient is larger than the standard value O.

Tire condition evaluation section 138 determines grade information, which is an evaluation index indicating the slip tendency of the tires of host vehicle 101, by referring to acquired statistical map 172. More specifically, tire condition evaluation section 138 maps the friction coefficient calculated by friction coefficient calculation section 133 and the tire condition coefficient calculated by tire condition coefficient calculation section 134 to statistical map 172, and determines the grade information based on the region on statistical map 172 where the data obtained by mapping exists.

The tire condition evaluation unit 138 sets the grade information to grade a (slip level: large) when the data obtained by establishing the map exists in the first zone a, sets the grade information to grade B (slip level: medium) when the target data exists in the second zone B, and sets the grade information to grade C (slip level: small) when the target data exists in the third zone C, for example. In this way, since the tire condition evaluation unit 138 determines the degree of slip of the tire of the host vehicle 101 based on the statistical map 172 generated from the collected data 160 concerning the plurality of other vehicles 105, the degree of slip of the tire of the host vehicle 101 can be objectively evaluated.

The notification unit 139 notifies the driver of the grade information obtained by the tire condition evaluation unit 138 as the determination result. The notification means 139 may notify the driver of the information by displaying, for example, attention information indicating that the tire is likely to slip on the display unit 122, or may notify the driver of the information as sound information. This can prompt the driver to drive safely.

As shown in fig. 9, the information collection server 106 includes: a communication unit 161 that transmits and receives information to and from the host vehicle 101 and the plurality of other vehicles 105; a control unit 162 that executes arithmetic processing based on information collected via the communication unit 161; and a storage unit 163 storing a program 171 executed by the control unit 162.

The control unit 162 of the information collection server 106 includes: a receiving unit 151 that receives the collected data 160 via a communication section 161; a collected data extracting unit 152 that extracts data from the collected data 160 under a predetermined extraction condition; a statistical map generating unit 153 that generates a statistical map 172 based on the extracted data extracted by the collected data extracting unit 152; storage section 154 that stores generated statistical map 172 in storage section 163; and a transmission unit 155 that transmits the statistical map 172 to the vehicle.

The collected data extraction unit 152 extracts data of the same vehicle type and position information as the host vehicle 101 and the same road surface condition as the host vehicle 101 from the collected data 160. The extraction conditions are not limited to these, and for example, the collected data extraction unit 152 may extract data of at least the same vehicle type as the host vehicle 101, or may extract data of at least the same position information as the host vehicle 101.

The statistical map generation unit 153 generates the statistical map 172 based on the tire condition coefficient and the friction coefficient of the plurality of pieces of extracted data extracted by the collected data extraction unit 152.

Transmission section 155 reads statistical map 172 from storage unit 163, and transmits transmission data generated based on read statistical map 172 to host vehicle 101 via communication unit 161.

Next, the processing contents of the road surface friction coefficient prediction system SYS101 according to the present embodiment will be described with reference to fig. 12. Fig. 12 is a flowchart showing an example of processing performed by the control unit 103 of the vehicle 101 and the control unit 62 of the information collection server 106.

The control unit 103 of the host vehicle 101 first acquires the position information indicating the current position of the host vehicle 101 generated by the position detection unit 124 (step S110). Then, the control unit 103 estimates road surface conditions (dry, wet, and snow) based on the weather information acquired from the weather information server 181 of the external device 109, and estimates a road state based on the road information (paved and unpaved) acquired from the road information server 182 (step S111).

Next, the control unit 103 of the host vehicle 101 calculates a road surface friction coefficient at the running position based on the running information indicating the running state of the host vehicle 101 acquired from the running information detection unit 123 (step S112), and calculates a tire condition coefficient based on the calculated friction coefficient and the reference friction coefficient of the reference map 142 stored in the storage unit 104 (step S113). Then, the control unit 103 acquires the road surface condition at a position forward in the traveling direction of the vehicle, and predicts the friction coefficient of the road surface forward in the traveling direction based on the reference friction coefficient and the tire condition coefficient according to the acquired road surface condition (step S114). The control unit 103 transmits the friction coefficient and the tire condition coefficient calculated as described above and vehicle information (vehicle ID, vehicle type, vehicle speed, and the like) relating to the host vehicle 101 to the information collection server 106 of the external device 109 (step S115).

The control unit 162 of the information collection server 106 receives the collected data 160 transmitted from the own vehicle 101 and the plurality of other vehicles 105 (step S120), and generates the statistical map 172 based on the collected data 160 (step S121). The control unit 162 stores the generated statistical map 172 in the storage unit 163 (step S122), and transmits the statistical map 172 to the vehicle side (step S123). This ends the processing of the information collection server 106.

The control unit 103 acquires the statistical map 172 transmitted from the information collection server 106 (step S116), and obtains grade information, which is an evaluation index of the slip tendency of the tire condition of the vehicle 101, by referring to the acquired statistical map 172 (step S117). If the level information is the level a or the level B (step S118), the driver is notified of the attention information indicating that the tire is in the slip-prone state (step S119). The determination condition in step S118 is not limited to this, and for example, the attention information may be notified only when the level information is a, or the attention information of different contents may be notified when the level a is different from the level B. On the other hand, if the level information is not level a or level B, the control unit 103 ends the processing as it is.

(action and Effect of the embodiment)

According to the above-described embodiment, since the road surface friction coefficient prediction system SYS101 predicts the friction coefficient between the tire and the road surface in the front in the traveling direction of the vehicle based on the tire condition coefficient indicating the state of the tire and the road surface condition, the road surface friction coefficient can be accurately calculated even when the road surface condition at the vehicle traveling position changes.

Further, according to the present embodiment, the road surface friction coefficient prediction system SYS101 can obtain the level information as the index value indicating the slip factor of the tire of the host vehicle 101 based on the statistical map 172 generated from the tire condition coefficients and the friction coefficients of the plurality of other vehicles 105 that are of the same vehicle type and travel at the same position as the host vehicle 101. Thus, road surface friction coefficient prediction system SYS101 can notify the driver of objective information indicating the degree of slip of the tires of host vehicle 101.

Although the case where the friction coefficient prediction unit 135 predicts the friction coefficient of the road surface at the position ahead of the vehicle of the host vehicle 101 in the traveling direction has been described, the friction coefficient prediction unit 135 may predict the road surface friction coefficient of the parking position during parking of the host vehicle 101.

In this case, the friction coefficient prediction unit 135 predicts the friction coefficient at the parking position of the own vehicle 101 based on the road surface condition at the current position acquired by the external information acquisition unit 131 immediately before the own vehicle 101 starts to start. For example, when the ignition is ON from the parking state in which the ignition of the host vehicle 101 is OFF, the friction coefficient prediction unit 135 acquires a reference friction coefficient corresponding to weather information at the time point when the ignition is ON from the reference map 142, and multiplies the reference friction coefficient by the tire condition coefficient to predict the road surface friction coefficient at the parking position. Thus, the road surface friction coefficient prediction system SYS101 can accurately predict the road surface friction coefficient even when the road surface condition changes during the stop of the vehicle. The road surface condition at the time point when the igniter is turned ON may be compared with the road surface condition immediately before the igniter is turned OFF, and if the comparison result is the same, the friction coefficient predicted when the igniter is turned OFF may be directly used as the predicted friction coefficient.

[ third embodiment ]

A third embodiment of the present disclosure will be described with reference to fig. 13 to 22.

Fig. 13 is a configuration diagram showing an overall schematic example of a traction performance evaluation system according to a third embodiment of the present disclosure.

As shown in fig. 13, a traction performance evaluation system SYS201 includes: a host vehicle 201 to be evaluated; a plurality of other vehicles 205; and an external device 209 communicably connected to the host vehicle 201 and the plurality of other vehicles 205 via a wireless communication network 290.

In the present embodiment, the host vehicle 201 is distinguished from the plurality of other vehicles 205 with respect to the vehicle for convenience of explanation, but the plurality of other vehicles 205 may be evaluation targets, and the host vehicle 201 and the plurality of other vehicles 205 correspond to "target vehicles" in the present disclosure.

The external device 209 includes: an information collection server 206 that collects vehicle information of the host vehicle 201 and a plurality of other vehicles 205; a weather information server 281; a road information server 282; and a GPS 283.

The weather information server 281 is a server that provides weather information of japan acquired from weather stations and the like in various places. The road information server 282 is a server that provides information indicating a road state (for example, a paved road) according to the current position where the vehicle is traveling. The weather information provided by the weather information server 281 and the road information provided by the road information server 282 are examples of disturbance elements that affect the condition of the road surface on which the vehicle is traveling.

Fig. 14 is a configuration diagram showing a schematic configuration example of the own vehicle 201 according to the present embodiment. This vehicle 201 is a four-wheel drive vehicle in which the distribution of the drive force can be variably performed from a four-wheel drive state in which the drive force is transmitted to the front wheels and the rear wheels to a two-wheel drive state in which the drive force is transmitted only to the front wheels. The plurality of other vehicles 205 also have the same configuration as the host vehicle 201 described with reference to fig. 14.

As shown in fig. 14, the vehicle 201 includes: an engine 211 as a driving source that generates driving force (torque) for traveling; a transmission 212 that changes the speed of the output of the engine 211; a pair of left and right

front wheels

210L and 210R as main drive wheels to which the driving force of the engine 211 shifted by the transmission 212 is transmitted at all times; a pair of left and right

rear wheels

220L, 220R as sub-drive wheels to which the driving force of the engine 211 is transmitted according to the vehicle state.

Further, the host vehicle 201 includes: a front differential 213 that differentially distributes the output of the engine 211 to the

front wheels

210L and 210R and transmits the distributed output to a propeller shaft 214; a rear differential 215 that differentially distributes the rotational force of the propeller shaft 214 to the

rear wheels

220L, 220R; left and right front wheel

side drive shafts

361, 362; left and right rear wheel-

side drive shafts

371, 372; a drive force transmission device 202 disposed between the propeller shaft 214 and the rear differential 215; and a control device 203 that controls the driving force transmission device 202.

The control device 203 CAN obtain various detection values including detection values of rotation speed sensors 301 to 304 for detecting rotation speeds of the left and right

front wheels

210L and 210R and the left and right

rear wheels

220L and 220R, an accelerator pedal sensor 305 for detecting a stepping amount of an accelerator pedal 310, and a steering angle sensor 306 for detecting a steering angle of a steering wheel 380, directly from the respective sensors or via a vehicle Network such as a Controller Area Network (CAN), and supply a current to the driving force transmission device 202 based on the detection values and the like. Information represented by the detection values obtained from the rotation speed sensors 301 to 304, the accelerator pedal sensor 305, and the steering angle sensor 306 is an example of "traveling information" in the present disclosure. Details of the control device 203 will be described later.

The driving force transmission device 202 increases or decreases the driving force transmitted to the left and right

rear wheels

220L and 220R in accordance with the current supplied from the control device 203. The drive force transmission device 202 includes a housing 221, a cylindrical output shaft 222 supported on the same shaft as the housing 221 so as to be relatively rotatable, a multiple disc clutch 223 housed in the housing 221, and an actuator 224 pressing the multiple disc clutch 223. The multiple disc clutch 223 includes a plurality of outer clutch discs 223a that rotate integrally with the housing 221 and a plurality of inner clutch discs 223b that rotate integrally with the output shaft 222, and receives the pressing force of the actuator 224 to bring the outer clutch discs 223a into frictional contact with the inner clutch discs 223 b.

Fig. 15 is a block diagram showing the configuration of the control device 203. Fig. 16 is a block diagram showing the configuration of the information collection server 206 of the external device 209.

As shown in fig. 15, the control device 203 includes: a communication unit 230 that transmits and receives information to and from the plurality of other vehicles 205 and the external device 209 via the wireless communication network 290; a control unit 231 including a CPU and its peripheral circuits; a storage unit 232 including a storage element such as a ROM or a RAM; and a current output circuit 233 for outputting a current to the actuator 224 of the driving force transmission device 202.

The control device 203 is connected to a display unit 241 for displaying information output from the control unit 231, a travel information detection unit 242 for detecting travel information indicating a travel state of the host vehicle 201, and a position detection unit 243 for detecting a current position of the host vehicle 201.

The display unit 241 displays information output from the control unit 231. The display unit 241 is a display such as a liquid crystal display or an organic EL display, and may function as a display unit of a car navigation system or may be provided on a control panel of a vehicle.

The travel information detection unit 242 is configured by a plurality of sensors for acquiring parameters of the travel state of the host vehicle 201, such as the rotation speed sensors 301 to 304, the accelerator pedal sensor 305, and the steering angle sensor 306.

The position detection unit 243 is a GPS receiver configured to acquire position information indicating the current position of the vehicle 201, and is a GPS receiver configured to acquire the current position information (such as the longitude and latitude) of the vehicle 201 using a satellite positioning system.

The communication unit 230 is an electronic control device that performs transmission and reception of information by communicating with a communication destination other than the host vehicle 201 via the wireless communication network 290. The communication unit 230 is constituted by a communication module such as DCM, for example.

The control unit 231 controls the driving force transmission device 202 by executing the program 320 stored in the storage unit 232. The storage unit 232 stores a torque map 321 in addition to the program 320. The torque map 321 defines map information for calculating the driving force to be distributed to the left and right

rear wheels

220L and 220R, based on, for example, the front-rear wheel rotation speed difference, which is the difference between the average rotation speed of the left and right

front wheels

210L and 210R and the average rotation speed of the left and right

rear wheels

220L and 220R, the depression amount and the steering angle of the accelerator pedal 310, and the vehicle speed.

The control unit 231 refers to the torque map 321 based on the vehicle running state, and calculates a command current corresponding to the driving force to be distributed to the left and right

rear wheels

220L and 220R. Then, the control unit 231 generates a PWM signal so that a current corresponding to the command current is output from the current output circuit 233 to the driving force transmission device 202.

The control unit 231 of the control device 203 includes an external information acquisition means 311, a position information acquisition means 312, a slip ratio calculation means 313, a command torque calculation means 314, a transmission means 315, a reception means 316, a notification means 317, and a command torque correction means 318.

The external information acquisition unit 311 estimates the road surface condition based on weather information supplied from the weather information server 281 of the external device 209. For example, when the weather information is sunny, the external information acquisition unit 311 estimates that the road surface condition is dry, and when the weather information is rainy, the external information acquisition unit 311 estimates that the road surface condition is wet. Then, external information acquisition section 311 acquires information indicating the road state (paved road or unpaved road) based on the road information provided from road information server 282.

Position information acquisition section 312 acquires position information generated by position detection unit 243.

Slip ratio calculation unit 313 calculates a slip ratio based on the running information relating to the running state of the vehicle detected by running information detection portion 242. The slip ratio can be calculated, for example, based on the wheel speeds detected by the rotational speed sensors 301 to 304 and an estimated vehicle body speed calculated based on the wheel speeds. Also, the slip ratio may be calculated based on the difference between the rotation speeds of the front and rear wheels.

Command torque calculation section 314 calculates a command torque to be transmitted by driving force transmission device 202 based on the detection result of travel information detection unit 242.

The transmitting unit 315 transmits the information related to the traction performance to the information collection server 206 through the communication unit 230. The transmission unit 315 generates transmission data based on the slip ratio calculated by the slip ratio calculation unit 313, the command current value calculated by the command torque calculation unit 314, vehicle information (vehicle ID, vehicle type, and the like) related to the own vehicle 201, position information, road surface information, and weather information, and transmits the transmission data to the information collection server 206 of the external device 209. The transmission data corresponds to a part of the collected data 260 collected by the information collection server 206.

Fig. 16 is a table showing an example of collected data 260. As shown in fig. 16, the collected data 260 has, as items, a vehicle ID for identifying the vehicle, vehicle type information related to the vehicle type of the vehicle, position information indicating the current position at which the vehicle travels, a road state and a road surface condition at a position indicated by the position information, and a friction coefficient, a slip ratio, and a command current value calculated for each vehicle. The items of the collected data 260 are merely examples, and are not limited thereto, and may include information such as the measurement date and time and the travel distance.

The reception unit 316 receives the evaluation result 273 of the traction performance evaluation unit 254 and the determination result of the deterioration degree determination unit 256 from the information collection server 206 described later.

The notification unit 317 notifies the driver of the grade information as the evaluation result 273 obtained by the reception unit 316. The notification unit 317 displays inspection information indicating, for example, tire replacement, deterioration of the vehicle, and the like, as notice information indicating that the host vehicle 201 is likely to slip on the display unit 241, and notifies the driver of the information. This can prompt the driver to drive safely.

Further, the notification unit 317 notifies the driver of the fact that the grade information is rapidly decreasing as a result of the determination by the deterioration degree determination unit 256. This makes it possible to notify the driver of the abnormality, thereby making it possible to promote safe driving or provide the driver with information to the effect that repair is necessary.

Command torque correction section 318 calculates a command current value of the control current to be supplied to driving force transmission device 202 based on the command torque, and corrects the calculated command current value based on the level information obtained by traction performance evaluation section 254 of information collection server 206. Details regarding the command torque correction unit 318 are described later.

As shown in fig. 17, the information collection server 206 includes: a communication unit 261 that transmits and receives information to and from the host vehicle 201 and the plurality of other vehicles 205; a control unit 262 that executes arithmetic processing based on information collected via the communication unit 261; and a storage unit 263 for storing a program 271 to be executed by the control unit 262. The information collection server 206 receives not only the transmission data transmitted by the transmission means 315 of the control unit 231 of the control device 203 but also the same data as the transmission data from the plurality of other vehicles 205 and collects the received data as the collected data 260.

The control unit 262 of the information collection server 206 includes: a receiving unit 251 that receives the collected data 260 collected from the host vehicle 201 and the other vehicles 205 via the communication unit 261; a collected data extracting unit 252 that extracts data from the collected data 260 under a predetermined extraction condition; a statistical map generating unit 253 that generates a statistical map 272 based on the extracted data extracted by the collected data extracting unit 252; a traction performance evaluation unit 254 that evaluates traction performance based on the statistical map 272; a memory cell 255; a deterioration progress degree determination unit 256 that determines the progress degree of deterioration of traction performance; a transmission unit 257 that transmits the evaluation result 273 of the traction performance evaluation unit 254 and the determination result of the deterioration degree of progress determination unit 256 to the vehicle; and an aged deterioration data generation unit 258 that generates aged deterioration data based on the data stored in the storage unit 263.

The collected data extraction unit 252 extracts data having the same vehicle type and position information as the host vehicle 201 and the same road surface condition as the host vehicle 201 from the collected data 260. That is, the collected data extraction unit 252 extracts, from the collected data 260, information of a plurality of other vehicles 205 of the same vehicle type traveling at the same position as the host vehicle 201 and in the same environment (for example, a paved road or the like) as the host vehicle 201. Since the statistical map 272 is generated based on the extracted data thus extracted, the accuracy of the evaluation result 273 by the traction performance evaluation unit 254 improves. The extraction conditions of the collected data extraction unit 252 are not limited to these, and the collected data extraction unit 252 may extract data of at least the same vehicle type as the host vehicle 201, or may extract data of at least the same position information as the host vehicle 201.

Fig. 18 is a table showing an example of the statistical map 272. The statistical map 272 is data obtained by correlating the command torque and the slip ratio, and the horizontal axis represents the command torque and the vertical axis represents the slip ratio. The statistical map 272 is not limited to this as long as it is data that can evaluate the traction performance of the vehicle, and may be data obtained by relating the friction coefficient to the slip ratio, or data obtained by relating the slip ratio to the vehicle speed, for example.

Statistical map 272 sets predetermined standard value O and first threshold value S₁Fourth threshold S₄. The standard value O is a value determined based on, for example, performance evaluation of the vehicle at the time of factory shipment. First threshold value S₁Fourth threshold S₄Maps are built for slip ratio and command torque of collected data 260, andthe data obtained by the vertical mapping is a value determined by using a statistical method. First threshold value S₁Fourth threshold S₄The standard value O deviates from the predetermined value.

First threshold value S₁And a second threshold S₂The value of the slip ratio with respect to the command torque may be larger than the standard value O, and the first threshold value S₁Is greater than a second threshold value S₂Deviated from the standard value O. And, the third threshold S₃And a fourth threshold value S₄The value of the slip ratio with respect to the command torque may be smaller than the standard value O, and the fourth threshold value S₄Is greater than a third threshold value S₃Deviated from the standard value O.

Here, in statistical map 272, the slip ratio is compared with first threshold S₁The large area is set as a first zone A to be defined by a first threshold S₁And a second threshold S₂The enclosed region is set as a second zone B which is defined by a second threshold S₂And a third region C defined by the standard value O, and a third threshold value S₃And a fourth zone D defined by the standard value O, and a third threshold value S₃And a fourth threshold value S₄The enclosed region is set as a fifth zone E, and the slip ratio is set to be higher than a fourth threshold value S₄The small area is set as the sixth zone F. For example, when the value of the slip ratio corresponding to the command torque is present in the first zone a, the vehicle is in a state of being likely to slip, and when the value is present in the sixth zone F, the vehicle is in a state of being unlikely to slip.

The traction performance evaluation unit 254 evaluates the traction performance of the host vehicle 201 by comparing the slip ratio calculated by the slip ratio calculation unit 313 and the command torque calculated by the command torque calculation unit 314 with a statistical map 272 as a reference slip ratio. Specifically, the traction performance evaluation means 254 maps the calculated data of the slip ratio and the command torque to the statistical map 272, and determines the level information as the evaluation result 273 of the traction performance based on the terrain on the statistical map 272 where the calculated data exists.

The grade information is information to which a grade is added according to the traction performance of the host vehicle 201, and the traction performance evaluation unit 254 sets the grade information to grade a (slip level: large) when the calculated data exists in the first zone a of the statistical map 272, sets the grade information to grade B (slip level: medium) when the calculated data exists in the second zone B, and sets the grade information to grade C (slip level: small) when the calculated data exists in the third zone C, for example. In this way, since the traction performance evaluation unit 254 determines the degree of slip of the host vehicle 201 based on the statistical map 272 generated from the collected data 260 on the plurality of other vehicles 205, the traction performance of the host vehicle 201 can be objectively grasped.

The storage unit 255 stores the statistical map 272 and the grade information as the evaluation result 273 of the traction performance evaluation unit 254 in the storage unit 263.

The deterioration progress degree determination unit 256 compares the current evaluation result 273 evaluated by the traction performance evaluation unit 254 with the past evaluation result 273 stored in the storage unit 255, and determines the deterioration progress degree of the traction performance of the own vehicle 201 as the target vehicle based on the comparison result. That is, the deterioration progress degree determination means 256 determines the degree of progress of deterioration based on the variation of the evaluation result 273 of the traction performance over a predetermined period. In the present embodiment, when the level information as the evaluation result 273 is lowered by 2 levels within a predetermined period, the deterioration degree determination means 256 determines that the deterioration of the traction performance is present.

Fig. 19 is a coordinate showing an example of transition of the level information with the lapse of time. Fig. 19 shows transition of the rank information of arbitrary 2 vehicles for convenience of explanation, and the transition of the rank information on the first vehicle is shown by a solid line, and the transition of the rank information on the second vehicle is shown by a two-dot chain line.

As shown in fig. 19, in the case of the first vehicle shown by the solid line, at time t at the current time point when the own vehicle 201 travels₂And a time t of a past time point which is a predetermined time ahead from the time of the current time point₁Time t in between₃The level information is lowered from level C to level B at the time point of (1), and the level information is maintained in the state of level B until the time point of (2)Time t of the current time point₂Until now. Here, the predetermined time is set to, for example, 1 month to 6 months.

On the other hand, in the case of the second vehicle shown by the two-dot chain line, at time t at the present point in time₂From the time t of the past point in time₁Time t in between₄The level information is decreased from level C to level B, and then at time t of the current time point₂The level information is lowered from level B to level a.

Regarding the second vehicle, deterioration degree of progress determination unit 256 will be from time t at the current point in time₂Time t traced back to a predetermined time of a past time point₁The evaluation result 273 generated by the traction force performance evaluation unit 254 of (1) is set as the past evaluation result 273. The deterioration degree of progress determination means 256 acquires time t at the past time point from the storage unit 263₁The result of evaluation in the past 273. Then, chronological degradation degree of progress determination section 256 compares time t at the past time point₁Rating information (rating C) as a result of evaluation of the past 273 and time t at the current time₂The current evaluation result 273, i.e., the grade information (grade a) is compared. The aged deterioration degree of progress determination unit 256 transmits information indicating that there is a sharp change in the rank information to the host vehicle 201 via the transmission unit 257 based on the comparison result that the rank information is lowered by 2 ranks.

On the other hand, regarding the first vehicle, since the rank information is lowered by only 1 rank, the deterioration progress degree determination unit 256 determines that rapid deterioration has not occurred.

The aged deterioration data generation unit 258 generates aged deterioration data based on the stored data stored in the storage section 263. The stored data includes, for example, the slip ratio, the friction coefficient, the evaluation result, and the like calculated by the control unit 262 of the information collection server 206, and is stored in the storage unit 263.

Fig. 20 is a graph showing an example of aged deterioration data of the slip ratio with the lapse of time, more specifically, the lapse of several years of the slip ratio, and the vertical axis shows the slip ratio and the horizontal axis shows time. As shown in fig. 20, the slip ratio increases with the passage of time. That is, a situation in which the traction performance gradually deteriorates is shown.

This chronological degradation data enables visualization of the performance of the vehicle, improving convenience. For example, the time of tire replacement, the time of repair timing, and the reference of the evaluation amount at the time of vehicle resale can be indicated. In the above embodiment, the aged deterioration data is set to indicate transition of the slip ratio, but the aged deterioration data is not limited to this, and may be set to indicate transition of the grade information.

The predetermined threshold value may be displayed on a graph of the aged deterioration data. Thus, when the slip ratio that changes with age exceeds the threshold value, the driver can be notified of the fact that the time at which repair or replacement is necessary has come, for example.

Next, the command torque correction unit 318 of the control unit 231 of the control device 203 will be described. Command torque correction section 318 is provided with an I-T characteristic map 322 in which command torque T is associated with command current value I. Fig. 21 shows an example of the I-T characteristic map 322. The vertical axis of the I-T characteristic map 322 represents the command torque T, and the horizontal axis represents the command current value I. As shown in fig. 21, a target torque T obtained by vehicle evaluation at the time of vehicle shipment is set in the I-T characteristic map 322₀. Target torque T₀The command current value I is set to be larger as the absolute value of the command torque T is larger.

Command torque correction section 319 calculates a command current value by comparing the calculated command torque with I-T characteristic map 322, and corrects the command current value by multiplying the calculated command current value by a correction coefficient corresponding to the rank information. The correction coefficient can be obtained by referring to a correction coefficient map obtained by associating the level information with the correction coefficient in advance, for example. This correction coefficient is a value for correcting a deviation of the calculated data of statistical map 272 from standard value O. For example, when the rank information obtained by calculating the data is rank A, B or C, command torque correction section 319 multiplies the correction coefficient by the command current value to obtain target torque T₀Large output rotationMoment T₁(the two-dot chain line shown in FIG. 21).

Next, the processing of the traction performance evaluation system SYS201 according to the present embodiment will be described with reference to fig. 22. Fig. 22 is a flowchart showing an example of processing performed by the control unit 231 of the control device 203 of the vehicle 201 and the control unit 262 of the information collection server 206.

The control unit 231 first acquires the position information indicating the current position of the vehicle 201 generated by the position detection unit 243 (step S210), estimates the road surface conditions (dry, wet, and snow) based on the weather information acquired from the weather information server 281 of the external device 209, and estimates the road state based on the road information (paved and unpaved) acquired from the road information server 282 (step S211).

Next, the control unit 231 calculates the slip ratio and the command torque based on the travel information indicating the traveling state of the host vehicle 201 acquired from the travel information detecting unit 242 (steps S212 and S213), and transmits the calculated slip ratio and command torque and the vehicle information (vehicle ID, vehicle type, vehicle speed, and the like) related to the host vehicle 201 to the information collecting server 206 of the external device 209 (step S214).

Next, the control unit 231 receives the level information or a message indicating that there is progress of the deterioration from the information collection server 206 (step S215). Then, the control unit 231 notifies the driver of the attention information corresponding to the level information (step S216), and corrects the command torque based on the level information (step S217). Thereby, the control unit 231 of the host vehicle 201 ends the processing.

The control unit 262 of the information collection server 206 receives the collected data 260 from the host vehicle 201 and the plurality of other vehicles 205 (step S220), generates the statistical map 272 based on the collected data 260 (step S221), and stores the generated statistical map 272 in the storage unit 263 (step S222).

Next, the control unit 262 obtains the grade information of the host vehicle 201 based on the slip ratio and the command torque received from the control unit 231 of the host vehicle 201 in step S220 and the generated statistical map 272 (step S223). When the rank information is rank a or rank B (yes in step S225), the control unit 262 transmits the rank information to the control unit 231 of the host vehicle 201 (step S226). On the other hand, if the level information is not level A or level B (NO in step S225), the control unit 262 proceeds directly to the process in step S227.

In step S227, the control unit 262 determines whether or not the rank information has dropped by 2 ranks (step S227). In this processing, the deterioration degree of progress determination unit 256 performs determination based on comparison of the past grade information as the evaluation result 273 and the present grade information as the evaluation result 273.

When determining that the rank information has fallen by 2 ranks (yes in step S227), the control unit 262 transmits information indicating that there is a sharp fall in the rank information to the control unit 231 of the host vehicle 201 (step S228). On the other hand, when it is determined that the degradation of the rank information is less than 2 ranks (no in step S227), the control unit 262 generates aged deterioration data based on the data stored in the storage unit 263 (step S229), and the process is terminated as it is.

(action and Effect of the embodiment)

According to the embodiment described above, the traction performance evaluation system SYS201 evaluates the traction performance based on the slip ratio calculated in the host vehicle 201 and the statistical map 272 as the reference slip ratio corresponding to the external information such as the road surface condition and the road state, and therefore, the traction performance can be evaluated in consideration of the external elements. Thus, the traction performance evaluation system SYS201 can accurately grasp the traction performance of the host vehicle 201.

Further, according to the present embodiment, the traction performance evaluation system SYS201 notifies the driver of the level information in which the level is added to the traction performance based on the statistical map 272 of the plurality of other vehicles 205 that are the same vehicle type and travel at the same position as the own vehicle 201, and therefore, it is possible to provide the driver with objective information indicating the degree of slip of the tire. This can prompt the driver to drive safely, and can prevent an accident in the future.

In the above-described embodiment, only the control unit 231 of the host vehicle 201 among the host vehicle 201 and the plurality of other vehicles 205 has been described, but the plurality of other vehicles 205 may also be provided with a control unit having a similar configuration and be able to evaluate the traction performance. In this case, when the traction performance of any one of the plurality of other vehicles 205 is ranked as the rank a, the own vehicle 201 may be configured to detect the information. This makes it possible to notify the driver of the host vehicle 201 of the presence of a vehicle in which there is a risk of slipping around the host vehicle, thereby preventing an accident.

In addition, even in the same vehicle type, the slip factor of the vehicle is likely to vary due to factors such as the type of tires, the air pressure, and the deterioration of other components, but in the conventional driving force transmission device, the command torque is not controlled in consideration of these factors, and therefore it is difficult to accurately grasp the traction performance. In the present embodiment, the traction performance evaluation system SYS201 evaluates the traction performance based on objective data such as the statistical map 272 of information of a plurality of other vehicles 205 traveling in the same vehicle type and in the same environment as the host vehicle 201 (for example, traveling at the same position as the host vehicle 201 and having the same road surface condition), and thereby can accurately grasp the traction performance of the host vehicle 201 without considering the above-described elements in each vehicle.

In the above-described embodiment, since the control unit 262 includes the deterioration degree determination means 256 that determines the degree of progress of the deterioration of the traction performance, the degree of deterioration of the host vehicle 201 can be grasped by comparing the traction performance of the host vehicle 201 in the past with the traction performance of the host vehicle 201 in the present. This can prompt the driver to drive safely, or prevent an accident by giving the driver a time for repair. Namely, the safety is improved.

Here, the traction performance evaluation system SYS201 and the host vehicle 201 according to the above-described embodiment can be summarized as [1] to [13] below.

[1] A traction performance evaluation system is provided with:

an external information acquisition unit that acquires external information relating to an interference element that affects a condition of a road surface on which a target vehicle is traveling;

a slip ratio calculation unit that calculates a slip ratio of a tire based on running information indicating a running state of the target vehicle; and

and a traction performance evaluation unit that evaluates the traction performance of the target vehicle based on a reference slip ratio corresponding to the external information and the slip ratio calculated by the slip ratio calculation unit.

[2] The traction performance evaluation system according to [1], wherein the traction performance evaluation unit evaluates the traction performance based on slip rates of tires of a plurality of vehicles of the same vehicle type as the subject vehicle.

[3] The traction performance evaluation system according to [1], wherein the traction performance evaluation unit evaluates the state of the tire based on slip rates of a plurality of vehicles of the same vehicle type as the subject vehicle.

[4] The traction performance evaluation system according to any one of [1] to [3], wherein the subject vehicle is communicable with an external device that collects travel information from the plurality of vehicles, and the external device has the traction performance evaluation unit and transmits an evaluation result evaluated by the traction performance evaluation unit to the subject vehicle.

[5] The traction performance evaluation system according to any one of [1] to [3], wherein the subject vehicle has the traction performance evaluation unit.

[6] The traction performance evaluation system according to [1], wherein the external information includes at least any one of weather information and road information.

[7] The traction performance evaluation system according to any one of [1] to [6], wherein the traction performance evaluation system includes a notification unit that notifies a driver of the target vehicle of an evaluation result of the traction performance evaluation unit.

[8] The traction performance evaluation system according to [1], further comprising: a storage unit that stores the evaluation result of the traction performance evaluation unit; and a deterioration degree of progress determination unit that compares the current evaluation result evaluated by the traction performance evaluation unit with the past evaluation result stored in the storage unit, and determines a deterioration degree of progress of the traction performance of the target vehicle based on the comparison result.

[9] The traction performance evaluation system according to [8], wherein the evaluation result of the traction performance evaluation means is level information to which a level is added according to the traction performance of the target vehicle, and the traction performance evaluation system further includes a notification means that notifies a driver of the target vehicle when the degradation degree determination means determines that the level information is decreased within a predetermined time.

[10] The traction performance evaluation system according to [8] or [9], wherein the subject vehicle is communicable with an external device that collects travel information from the plurality of vehicles, the external device having the degradation degree of progress determination unit that transmits information indicating the degree of progress of degradation determined based on the evaluation results of the plurality of vehicles by the traction performance evaluation unit to the subject vehicle.

[11] The traction performance evaluation system according to any one of [8] to [10], wherein the deterioration progress degree determination unit determines the deterioration progress degree of the traction performance based on evaluation results of a plurality of vehicles of the same vehicle type as the subject vehicle.

[12] The traction performance evaluation system according to [8] or [9], wherein the subject vehicle has the deterioration progress degree determination unit.

[13] A four-wheel drive vehicle is provided with: a main drive wheel to which a drive force of a drive source is always transmitted and an auxiliary drive wheel to which the drive force of the drive source is transmitted according to a vehicle state; a drive force transmission device interposed on a drive force transmission path to the auxiliary drive wheel; and a control device that controls the driving force transmission device according to the vehicle state, the control device being capable of acquiring an evaluation result of the traction force performance evaluation means in the traction force performance evaluation system according to any one of [1] to [12], and controlling the driving force transmission device based on the evaluation result.

(attached note)

Although the embodiments of the present disclosure have been described above, the embodiments described above do not limit the invention according to the claims. Note that all combinations of the features described in the embodiments are not essential to the means for solving the problem of the invention.

In the above-described embodiment, only the

control units

3, 103, and 231 of the

host vehicle

1, 101, and 201 among the

host vehicle

1, 101, and 201 and the plurality of

other vehicles

5, 105, and 205 have been described, but the plurality of

other vehicles

5, 105, and 205 also have control units having the same configuration and can determine the state of the tire. In this case, the

host vehicle

1, 101, 201 may be configured to detect the level information of the plurality of

other vehicles

5, 105, 205 when a vehicle whose level information is level a or level B is present. This makes it possible to notify the driver of the

host vehicle

1, 101, 201 of the presence of a vehicle in which there is a risk of slipping around the host vehicle, thereby preventing an accident.

In the above-described embodiment, the

control units

3 and 103 of the own vehicles 1 and 101 determine the grade information by the tire

condition evaluation units

37 and 138, but the

control units

62 and 162 of the

information collection servers

6 and 106 may determine the grade information. In this case, the transmission means 55, 155 of the

control units

62, 162 of the

information collection servers

6, 106 transmit only the grade information to the own vehicles 1, 101, and the notification means 38, 139 of the

control units

3, 103 of the own vehicles 1, 101 notify the driver of the attention information based on the received grade information. In the above embodiment, the control unit 262 of the information collection server 206 determines the grade information by the traction performance evaluation means 254, but the control unit 231 of the host vehicle 201 may determine the grade information. In the above-described embodiment, the control unit 262 of the information collection server 206 detects a rapid change in the level information by the degradation degree determination means 256, but the control unit 231 of the own vehicle 201 may detect a rapid change in the level information. That is, the traction performance evaluation means 254 and the deterioration degree determination means 256 may be mounted on the control unit 231 of the control device 203 of the host vehicle 201 or may be mounted on the control unit 262 of the information collection server 206.

In the present disclosure, the

information collection servers

6, 106, and 206 of the

external devices

9, 109, and 209 are not essential components. That is, in the above-described embodiment, the

statistical maps

72 and 172 are generated based on the collected

data

60 and 160 by the

information collection servers

6 and 106 of the

external devices

9 and 109, but the

statistical maps

72 and 172 may be generated by receiving the collected

data

60 and 160 from the plurality of

other vehicles

5 and 105 on the own vehicle 1 or 101 side. In the above embodiment, the information collection server 206 of the external device 209 generates the statistical map 272 based on the collected data 260, and performs the evaluation of the traction performance and the determination of the degree of progress of degradation based on the statistical map 272.

In the above embodiment, the

statistical maps

72 and 172 have the first threshold S₁And a second threshold S₂These 2 thresholds, statistical mapping 272 has a first threshold S₁Fourth threshold S₄These 4 thresholds are not limited to the above, but the number of thresholds may be 3 or 6, for example.

In the above-described embodiment, the

control units

3 and 103 acquire the travel information from the travel

information detection units

23 and 123 composed of a plurality of sensors, but the parameters of the travel state may be acquired from another control device, not shown, included in the own vehicle 1 or 101 via an in-vehicle network. Further, the control device 203 acquires various sensor detection values, but may acquire calculation values calculated by another control device not shown included in the host vehicle 201 via an onboard network such as CAN.

Claims

1. A road surface friction coefficient prediction system is provided with:

a tire information acquisition unit that acquires tire information indicating a condition of a tire of the target vehicle; and

a friction coefficient prediction unit that predicts a friction coefficient between the tire and the road surface based on the tire information acquired by the tire information acquisition unit and the external information acquired by the external information acquisition unit,

the friction coefficient prediction unit predicts a friction coefficient of a road surface ahead of the target vehicle in a traveling direction.

2. The road surface friction coefficient prediction system according to claim 1,

the external information includes at least any one of weather information and road information.

3. The road surface friction coefficient prediction system according to claim 1,

the tire information acquisition means acquires the tire information based on a coefficient of friction between tires of a plurality of preceding vehicles and a road surface.

4. The road surface friction coefficient prediction system according to any one of claims 1 to 3,

the friction coefficient prediction unit predicts a friction coefficient of a road surface at a parking position of the subject vehicle based on the external information acquired immediately before the subject vehicle starts.